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Rounding Off and Estimation Worksheet

Mental maths lesson 15: Rounding off and best estimate · Set 443 · 40 questions
TalentJR

How to do it in your head (Round, then work): Round each number: 2-digit numbers to the nearest ten, 3-digit numbers to the nearest hundred. Do the easy sum with the round numbers. Choose the option closest to your estimate.

NameDateTime takenScore ___ / 40
  1. 1.Best estimate of 40 × 37? (a) 1600 (b) 16000 (c) 160
  2. 2.Best estimate of 81 × 29? (a) 2400 (b) 240 (c) 24000
  3. 3.Best estimate of 79 × 57? (a) 480 (b) 48000 (c) 4800
  4. 4.Best estimate of 781 + 831? (a) 1600 (b) 1800 (c) 1400
  5. 5.Best estimate of 86 × 93? (a) 81000 (b) 8100 (c) 810
  6. 6.Best estimate of 129 + 561? (a) 700 (b) 500 (c) 900
  7. 7.Best estimate of 532 + 741? (a) 1000 (b) 1400 (c) 1200
  8. 8.Best estimate of 394 + 271? (a) 900 (b) 700 (c) 500
  9. 9.Best estimate of 56 × 91? (a) 540 (b) 5400 (c) 54000
  10. 10.Best estimate of 263 + 723? (a) 800 (b) 1000 (c) 1200
  11. 11.Best estimate of 66 × 37? (a) 2800 (b) 280 (c) 28000
  12. 12.Best estimate of 18 × 36? (a) 8000 (b) 80 (c) 800
  13. 13.Best estimate of 82 × 27? (a) 2400 (b) 240 (c) 24000
  14. 14.Best estimate of 20 × 72? (a) 140 (b) 1400 (c) 14000
  15. 15.Best estimate of 427 + 771? (a) 1400 (b) 1000 (c) 1200
  16. 16.Best estimate of 26 × 89? (a) 27000 (b) 2700 (c) 270
  17. 17.Best estimate of 31 × 74? (a) 2100 (b) 210 (c) 21000
  18. 18.Best estimate of 563 + 236? (a) 800 (b) 1000 (c) 600
  19. 19.Best estimate of 96 × 92? (a) 9000 (b) 900 (c) 90000
  20. 20.Best estimate of 242 + 155? (a) 600 (b) 200 (c) 400
  21. 21.Best estimate of 12 × 73? (a) 70 (b) 700 (c) 7000
  22. 22.Best estimate of 78 × 89? (a) 7200 (b) 72000 (c) 720
  23. 23.Best estimate of 123 + 592? (a) 500 (b) 900 (c) 700
  24. 24.Best estimate of 281 + 530? (a) 800 (b) 1000 (c) 600
  25. 25.Best estimate of 43 × 70? (a) 2800 (b) 280 (c) 28000
  26. 26.Best estimate of 457 + 811? (a) 1500 (b) 1300 (c) 1100
  27. 27.Best estimate of 12 × 51? (a) 500 (b) 50 (c) 5000
  28. 28.Best estimate of 18 × 24? (a) 400 (b) 4000 (c) 40
  29. 29.Best estimate of 665 + 381? (a) 1300 (b) 1100 (c) 900
  30. 30.Best estimate of 205 + 135? (a) 300 (b) 500 (c) 100
  31. 31.Best estimate of 56 × 36? (a) 240 (b) 24000 (c) 2400
  32. 32.Best estimate of 13 × 46? (a) 500 (b) 5000 (c) 50
  33. 33.Best estimate of 33 × 22? (a) 600 (b) 6000 (c) 60
  34. 34.Best estimate of 183 + 175? (a) 200 (b) 400 (c) 600
  35. 35.Best estimate of 46 × 23? (a) 100 (b) 10000 (c) 1000
  36. 36.Best estimate of 74 × 76? (a) 56000 (b) 5600 (c) 560
  37. 37.Best estimate of 96 × 39? (a) 40000 (b) 4000 (c) 400
  38. 38.Best estimate of 658 + 793? (a) 1700 (b) 1500 (c) 1300
  39. 39.Best estimate of 48 × 33? (a) 15000 (b) 1500 (c) 150
  40. 40.Best estimate of 81 × 16? (a) 16000 (b) 160 (c) 1600

Answer key

  1. 1600
  2. 2400
  3. 4800
  4. 1600
  5. 8100
  6. 700
  7. 1200
  8. 700
  9. 5400
  10. 1000
  11. 2800
  12. 800
  13. 2400
  14. 1400
  15. 1200
  16. 2700
  17. 2100
  18. 800
  19. 9000
  20. 400
  21. 700
  22. 7200
  23. 700
  24. 800
  25. 2800
  26. 1300
  27. 500
  28. 400
  29. 1100
  30. 300
  31. 2400
  32. 500
  33. 600
  34. 400
  35. 1000
  36. 5600
  37. 4000
  38. 1500
  39. 1500
  40. 1600

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